Itching or pruritis is a common dermatologic symptom. The causes of pruritis are complex and poorly understood. The best understood mechanism of itching is the release of histamine in the skin leading to urticarial wheals and intense itching. Such itching has traditionally been relieved by antihistamines. While antihistamine therapy is often effective, the sedation and drowsiness produced by antihistaminic agents limits their effectiveness.
Many kinds of itching are not however easily relieved by antihistamines. For example, conditions such as Hodgkin's Disease, mycosis fungoides (cutaneous malignancy) and severe jaundice produce intense itching unrelieved by antihistamines. Therefore, there is a need for improved treatment to relieve itching which can not only be an alternative to antihistaminic treatment of itching due to such causes as mosquitoe bites which responds to such treatment, but which further provides relief in intractable cases of pruritis which heretofore have been virtually impossible to treat except as disclosed in my prior U.S. Pat. No. 4,181,726 issued Jan. 1, 1980, a method based on the systemic effect on the central nervous system. The present invention provides such a composition and method independent of systemic effects on the central nervous system.
I have discovered surprisingly that tricyclic anti-depressants usually prescribed for ameliorating the effects of severe depression are effective at relieving itching when applied topically. These compounds include the pharmaceutically acceptable salts of the tricyclics. The term pharmaceutically acceptable salts, as used herein, refers to the physiologically acceptable acid addition salts such as the hydrochloride, hydrobromide, hydroiodide, acetate, valerate, oleate, etc. Doxepin, amitriptyline and imipramine respectively are the tertiary amine derivatives of dibenzoxepin, dibenzocycloheptadiene and dibenzazepine wherein the nitrogen atom is connected to the ring structure by a three carbon aliphatic chain and the tertiary amine has two carbon atoms attached thereto in addition to the aliphatic chain.
The present invention relates to a method and composition for topically treating pruritis.
A principal object of the present invention is topically to apply divided doses of tricyclic anti-depressant compounds traditionally employed systemically for treatment of mental depression to relieve pruritis.
Yet another object of the present invention is to provide a method and composition for treating pruritis wherein the tricyclic anti-depressant contains one of the following ring structures: ##STR1##
These and other objects of the present invention may be more readily understood when considered in conjunction with the following detailed description and examples.